Wild boar (Sus scrofa), sixth in our Black Dog Series, is a keystone ecosystem engineer that can influence a variety of ecological properties through rooting activity and as predators and prey. Wild boar primarily eat plants and share much in common with the ecological role of bears. They help disperse seeds, affect nutrient cycles that benefit trees, and can increase plant species and habitat richness when their densities are sustainable. Wild boar are also effective predators on a variety of prey – from earthworms to fawns – although their influence on prey populations is not well understood.

As they spread across the globe (both independently and with human assistance), they have formed symbiotic relationships with a variety of native species. For example, naturalised wild boar have formed symbiotic feeding-cleaning relationships with native birds that consume their ectoparasites. Boar-human symbiosis has a history dating back thousands of years, with evidence of domesticated boar (pigs) in Oceania, including Papua New Guinea, appearing between 10,000 and 3,000 years ago.

There is little known difference between the ecologies of wild boar in their native and introduced ranges, and their populations can irrupt in both locales in the absence of large predators. In their native range of Eurasia, wolves and tigers are important predators. In North America where they were introduced, wolves, cougars, black bears, coyotes and bobcats are boar predators, and in Australia dingoes limit their densities.

Wild boar quickly form complex interactions across the food web, forming ecological links with an immense variety of organisms from invertebrates, forbs, trees, small mammals, birds, reptiles, soil chemistry and to large predators. Activities aimed at boar control and eradication may therefore backfire with unintended consequences. A better option is to allow the predators of wild boar, such as dingoes, to thrive.